Broadcast paging system



NOV. 17, 1959 E, H, GATZERT EI'AL 2,913,533

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E. H. GATzERT ETA'L BROADCAST PAGING .SYSTEM Nov. 17, 1959 Filed Dec. 23, 1957 Nov. 17, 1959 E. H. GA'rzER-r Erm. 2,913,533

BROADCAST PAGING SYSTEM 6 sheets-sheet s Filed Dec. 23, 1957 IIQ/ /Eum

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BROADCAST PAGING 6 ShgQts-Sheet 4 Filed Dec. 23, 1957 Nov. 17, 1959 E, H, GATZRT EVAL BROADCAST PGING SYSTEM Filed Dec. as, 1957 6 Sheets+$heet 5 Nov. 17, 1959 E. H. GATzERT ETAL 2,913,533

BROADCAST PAGING SYSTEM Filed Dec. 23, 1957 6 Sheets--Sheet 6 United States BROADCAST'PAGING SYSTEM Application December 23, 1957, Serial No. 704,487

29 Claims. (Cl. 179-18) This invention relates to paging systems in general and more particularly to paging systems of the so-called meet me type.

A meet me paging system usually includes a first subsystem having a common signaling transmitter for signaling the required one of a plurality of stations within the subsystem. Selective control of the signaling transmitter may be effected by means such as an operator position or a subscriber controlled termination accessible from a dial telephone system. After having lcaused the transmitter to be selectively operated, the paging or calling party and the paged or called party at the required first subsystem station use a second subsystem for eX- tending connections from ones of a plurality of second subsystem stations to a common point in order to complete a connection between paging and paged parties. The usual connection provides for transmitting information in both directions. While such connections usually include a speech transmission channel, other modes of information transmission could be employed. Further, while such systems usually include separate and distinct first and second subsystems, our invention is directed to also include a communication system in which the first and second subsystems may take the form of first and second special use equipments within the same overall communication system.

When the above-referred to second subsystem takes the form of a dial telephone system, it is the usual practice to combine the first subsystem transmitter control equipment with the two-way connection access equipment in order to save apparatus and to minimize the number of operations to be carried out by a calling party required to complete a paging call. If such a system is adapted to handle-only one paging call at a time, access termination is madeaccessible at a first calling point from telephone system switching equipment. The switching equipment responds in the conventional manner to directive impulse trains from the calling line used by the paging party to establish a connection from the paging party station to the access termination. The access termination is thus seized and thereafter is responsive to further trains of directive impulses effective to control the first subsystem signal transmitter. The paged party, upon receiving a signal at the first subsystem station, takes-up any telephone within the second subsystem and extends a connection in the conventional manner'into a second, answering, point on the access termination. The extension of the last-mentioned connection is effective for causing the termination to complete a connection between the talking channels of the first and second termination access points, so that the paging and paged parties are connected to each other over a two-way communication channel.

While the simple system outlined above is practical to effect one paging call at a time, it is obvious that a system of greater capacity would be desirable. However, when the above-outlined system is expanded to provide for extending two or more calls at any one time, itis atent` O M 2,913,533 Patented Nov. 17, 19,59

.necessary to provide in the access equipment signal storage apparatus capable of recording the identity and access point of the calling party and the-identity of the iirst system station. The stored information is later used upon the completion of the called partys connection to the answering access point for directing auxiliary switching apparatus to complete a connection between the desired paging and paged parties. Such apparatus is necessarily complex, and further, a way must be found to identify a paged party upon the completion of the second subsystem connection to the signal storage equipment. The latter requirement, at best, complicates the operation of the paging system from the `subscribers point of view.

Accordingly, it is an object of our invention to provide a new and improved paging system.

Another object of our invention is to provide a new and improved paging system of the meet me type.

Another object of our invention is to provide a new and improved paging system wherein a private connection may be established between paging and paged parties.

Another object of our invention is to provide a new and improved paging system wherein a private connection between several pairs of paging and paged parties may be established at any one time.

Another object of our invention is to provide in a paging system a new and improved apparatus for responding to alarm Aor malfunction conditions within the paging system.

Weaccomplish these and other objects of our invention by providing a communication system having first and second subsystems. The first subsystem includes a common signal transmitting device such as a wireless transmitter and a plurality of receiving stations. Each of the first subsystem stations is assigned a unique directory number comprising oneror more digits. This first subsystem may be of the same general type as the one described in patent application Serial No. 432,517, led May 26, 1954, by John R. Scantlin and assigned to the same assignee as the present invention. The signal transmitting device is selectively operable for signaling any one of the receiving stations. The second subsystem includes a dial type telephone system.` The telephone system has an ofiice comprising switching equipment capable of the conventional use of extending connections between calling and called ones of a plurality of lines upon the manipulation of a dial or other signal transmitting device at the telephone station connected to the calling line. f

In ourV system, a person wishing to page any one of the first subsystem stations, picks up a second subsystem telephone, dials a special access (calling) code-and thereafter dials the directory number of the required .first subsystem station. The ofiice switching equipment has access to special equipment for controlling the first-sub- Y lsystem transmitter.

The special apparatus includes a first plurality of calling connectors and a second plurality of answering connectors. Each special apparatus connector has access to a plurality of terminal sets, the terminal sets accessible to each connector being connected in multiple to corresponding terminal sets accessible from the other connectors. Certain ones of each multipled terminalset` aren used for a speech transmission channel. The -dial ofiice apparatus is arranged so that when the party wishing to page dials the calling access number, a switch train is directively operated to select an idle one of the calling connectors. Thereafter, when the calling party dials the Y directory number of the required first subsystem station, the selected connector is directively operated tro-extend a connection from the calling line through the switch V'train including the selected one of the calling connectors to a particular one of the terminal sets, and, therefore, to a particular speech transmission channel. The calling station and line, and the office switching equipment, therefore, may be considered calling means for directively operating any one of the calling connectors.

The paged or called party at the signaled first subsystem station having been notified, by the use of the first subsystem in a manner to be described presently, that a paging party wishes to communicate with him, picks up an idle second subsystem vtelephone and dials another special access (answering) number and thereafter dials the directory number of hisown first subsystem station. Dialing the answering access number causes another dial oice switch train to be directively operated to select an idle one of the answering connectors. Thereafter, when the paged party dials further directive digits representing the directory number of the first subsystem, paged sta tion into the selected answering connector a connection is extended over the switch train including the selected one of the answering connectors from the paged partys station to the terminal set corresponding to the one selected by the operated calling connector, and, therefore, to the one of the speech transmission channels previously selected by the calling connector. Thereafter, conversation between the paging and paged parties takes place. Assuming that there are more sets of terminals accessible to each switch than the number of switches in either of the pluralities, it is thus possible to establish as many conversations between the calling and paged parties as there are pairs of calling and answering connectors.

In addition to its above-described function of establish-` ing a connection between the second subsystem stations, the calling connector is effective for causing start means within an encoder control common to the plurality of calling connectors to energize certain ones of the rionspeech transmission channel terminals within the set selected by the calling connector. These otherterminals within each set are unique to one of the plurality of first subsystem stations and when energized, are effective for selectively operating decoding means in accordance with the identity of this selected terminal set. The decoding means in turn is effective for selectively controlling tlie signal transmitting means within the first subsystem transmitter.

The transmitter includes means operative in response to a complete operation of its own signal transmitting means for operating end-of-cycle means. The operated end-of-cycle means is effective for causing means within the encoder control means to deenergize the selected one of the terminal sets in order to stop further operation of the transmitter. The encoder control means is then available for use by other of the calling connectors as the demand for the service of the encoder control means arises. With this arrangement, several of the callingconnectors can sequentially control the iirst subsystem transmitter within any given time interval.

In the following description, reference is made to the drawings attached to and forming a part of the present specification, and in which:

1 shows a block diagram of the system;

Fig. 2 shows a schematic diagram of an incoming paging connector;

Fig. 3 shows a schematic diagram of an incoming answering connector;

Figs. 4a and 4b show schematic diagrams of an intercept termination and an intercept answering device, respectively;

Figs. Sri-5f show schematic diagrams of the decoding matrices and encoder transmitter, and diode sets;

' Fig. 6 shows a schematic diagram of the encoder control;and

Fig 7 shows the order in which Figs. 2-6 are to be oriented.

AOursystern comprises vfirst and second subsystems. Thek first subsystem includes a plurality of stations and a transmitter common to the stations of the general type described by Iohn R. Scantlin in a patent application tiled May 26, 1954, Serial No. 432,517, and assigned to the saine assignee as the present invention. The transmitter is selectively operable in a .manner to be described for signaling any station within the system.

The apparatus in the following description of our invention is made to function fromv power supplied from various sources. A -rst power source is a battery having its most positive plate or terminal connected to ground. This plate is hereafter referred toas ground in the description and as (-1-) in the drawings. The other, most negative plate or terminal of the battery is referred to in the description as battery and in the drawings as Another power source is low impedance tone supply which produces a four hundred cycle per second signal. One side of the source is connected to the above-referred to ground, the other, ungrounded side being indicated as dial tone in both the drawings and description. The ungrounded tone supply conductor is also passed through an interrupter circuit of the well-known type and is delivered on a conductor indicated as busy tone both in the description and drawings at a frequency of 60 impulses per minute. The interrupter is also used for producing interrupted battery and ground signals, labeled 60 impulses per minute or as required. Another tone source having a first, grounded side, and a second, ungrounded side which is passed through the interrupter, provides an interrupted 20 cycle per second signal hereinafter referred to inthe description and drawings as ringback tone.

In the following description, reference to apparatus shown in the drawings includes a single digit followed by an identifying letter or letters and digits. The prei-ix digit refers to the iigure number in which the element is found, while the letters identify the element within the figure. The windings of multicontact relays are identitied as indicated above and are followed by a slash and an additional digit or digits indicating the number of contacts on the relay` Thus, 2GB/2 refers to the calling bridge relay having two sets of contacts appearing in Fig. 2, and ZCBi refers to a particular set of' contacts on relay 2GB.

Originating a paging call Referring to Fig. l, a first subsystem comprising a conventional local, dial telephone oiiice is indicated. The otiice has a plurality of lines such as 11.10 and 11.20. connected thereto. Stations, such as A and B, respectively, are connected to each of the lines. To originate a call from a line such as IL10, the telephone at station A is removed from its hookswitch, and thereafter a connection is extended by conventional methods to switching equipment within the .oiice such as selector 1810. The selector is thereupon directively operated by manipulating a ldial at station A so that the selectors `wiper set shown collectively as iWl is directively advanced into engagement with one of a plurality of terminal sets accessible from the selector. The office switching equipment is not described in detail here because its operation is well understood by those sliilled in the art, and because the otiice switching equipment per se does not form a part of our invention.

Assuming that the person at station A calling line 11.10 wishes to make a paging call, the signal transmitter at station A is manipulated so that selector 1810V is directed to a particular level wherein a first plurality of special switching connectors, such as the calling connector shown in Fig. 2 are terminated. The conductors, such as those shown collectively as 1G10, incoming to each calling connector are terminated on one of the terminal sets within the special level. Upon the sclection of the particular leve-l, the wiper set W10 of @selector 151i) is automatically advanced over `the terminal Vsets within the level until the wiper set engages the terminal set of an idle calling connector. Assuming that the one shown in Pig. 2 is the iirst idle connector encountered, seizure of that connector thereafter takes place in the manner next described.

Seizure of a calling connector.-Referring to Fig. 2, the extension of a connection to an idle connector such as the one shown in Fig. 2 is ellective for completing a talking channel from the conductors on line 1L10 to the talking channel of the calling connector which includes conductors 2T and 2R. The conventional short including the dial interrupter contacts between the conductors of line 1L10 at station A is effective for completing an operating circuit for calling bridge relay ZCB. The circuit is traced from ground through break contacts 2BT3 and 2AL1, the upper winding of relay ZCB, break contacts 2AN1, conductor 2T, the corresponding conductors through selector 1810 and line IL10, apparatus including the impulsing dial contacts of station A, the other talking conductors of line IL and selector 1810, conductor 2R, break contacts 2AN4, and the lower winding of relay ZCB to battery. Relay 2GB thereupon operates to complete an obvious operating circuit for release delay relay 2RD at make contacts 2CB1.

The operation of relay 2RD is etective for preparing a holding circuit for itself at make contacts 2RD1. The operation of relay 2RD is further effective for preparing an energizing circuit for each of the primary and secondary advancing means of the connector comprising primary magnet 2PM and second magnet ZSM, respectively, at make contacts ZRDZ. The operation of relay 2RD is further effective for placing a holding and busy marking ground on sleeve conductor 2S incoming conductors to the calling connector at make contacts ZRDS. Thereafter, the preceding switch train including selector 1810 is held and the calling connector of Fig. 2 is marked busy in the conventional manner by virtue of the grounded 2S conductor.

The operation of relay 2RD is further effective for opening the subsequently described operating circuit for release magnet 2RM at break contacts 2RD6. The operation of relay 2RD is further effective for completing an energizing circuit for monitor lamp 2ML from ground through break contacts 2AN9 and 2AL9, make contacts 2RD7, and the filament of lamp 2ML to battery. Lamp 2ML thereupon flows in full brilliance to indicate that a call is standing in on the connector.

The operation of relay 2RD is further eifective for operating primary and secondary delay relays 2PD and 2SD,

respectively. The operating circuit of relay 2PD is traced,

from ground through the contacts 2RD4, break contacts ZPONZ, and the upper winding of relay 2PD to battery. Relays 2PD and 2SD thereupon operate.

The operation of relay 2PD is effective for completing an auxiliary ground supply circuit for incoming sleeve conductor 2S at make contacts 2PD3 for reasons to be set forth under the description of the interrupt operation. The operation of relay 2PD is further etlective for preparing an operating circuit for primary magnet 2PM at make contacts 2PD]` and for operating an energizing circuit for secondary magnet ZSM at breach contacts 2PD2.

Advance of the calling connector in its primary direction-The seizure process of the calling connector is now completed, and the connector is ready to receive trains of directive impulses from calling station A over incoming conductors 2T and 2R. Each impulse in such a train is caused by the conventional opening and reclosing of the impulsing dial contacts at the station. As a result, lthe above-described circuit for operating relay 2CB is opened and reclosed and relay 2GB releases and reoperates in response to each such impulse. At the conclusion of each impulse train, relay ZCB comes to rest in its operated condition. Relay 2RD, a slow release type, does-not release during the time that impulses are being released by relay ZCB, even though the'above-described 6 operating circuit of relay 2RD is momentarily openedat make contacts 2CB1. v

During the transmission of a first train of impulses to the calling connector, that is during the time thatk both relays 2PD and ZSD are operated, a circuit is completed upon each release of relay ZCB for energizing means for advancing the Wiper set of the connector comprising wipers ZWT, ZWR, ZWS and ZWHS away from their normal position in a primary direction. rThe energizing circuit is completed from ground through break contacts ZCBZ, make contacts ZRDZ, 2SD1, and 2PD1, and the winding of magnet 2PM to battery. The b-attery-connected lower winding of relay 2PD is connected in parallel with magnet 2PM, so that the lower winding of relay 2PD is intermittently energized during the receipt of impulses at magnet 2PM. t

Each energization o f magnet 2PM is eiective for Va'dvancing t-he above-referred to wiper set one additional step away from its normal position. At any one ofthe advanced positions, the wiper set is opposite a corresponding level of the plurality of terminal sets to which the connector has access. The advance of a wiper set in its normal direction is further elective for operating the primary otE-normal springs of the connector, so that the above-referred to energizing circuit for relay 2PD-is opened at break contacts ZPONZ. Thereafter relay 2PD, a slow release type, is maintained in its operated condition by the intermittent energization of its lower'winding in the above-described manner. This intermittent energization of the lower winding stops upon receipt of the last impulse of the iirst train, so that relay V2PD thereafter releases. At this point, the wiper set has come to rest opposite the selected level of terminal sets.

The release of relay 2PD is effective toA prepare the connector to receive a second train of directive impulses from the calling line. To this end, the release of relay 2PD is eiective for disconnecting magnet 2PM and the lower winding of relay 2PD from vthe above-described impulsing circuit at make contacts 2PD1 and for preparing a circuit for energizing secondary magnet 2SM at break contacts 2PD2,

Advance of the calling connector ints secondary dectzon.-Upon the transmission .of'a second impulse train to the connectors, relay ZCB is again impulsed in its previously described manner and is eective for energizing secondary advancing means comprising magnet ZSM. The magnet is energized upon each release of relay ZCB over the following circuit: from ground through break contacts ZCBZ, make contacts 2RD2 and `2SD1, and break contacts 2PD2, and the winding of magnet ZSM to battery. The battery connectedkto the lower winding of relay 28B is connected in parallel with magnet ZSM, so that the lower winding of the relay is intermittently enfergized during the transmission of the second impulse train to the connector.

vEach energization of magnet ZSM is eflective for advancing the above-referred to wiper set away from its normal secondary position into engagement with successive ones of the contacts .in the selected one of the levels. Thus, at the endl of transmission ofl the second impulse train, the wiper set comes to rest in engagement. with a selected terminal set within the selected level. lEach terminal set within the plurality of sets accessible to each calling connector, such as the oner shown in Fig. 2 includes iirst and second talking channel terminals (to be engaged by wipers such as ZWT and ZWR), a busy test terminal (to be engaged by a wiper suchas 2WS) and a signaling terminal (to be engaged by a wiper such as 2WHS). f

Upon the iirst step of the wiper` set away from its normal secondary position, secondary off-normal means comprising contacts are operated in order to open the abovetraced operating circuit for relay. 2SD at break contacts 2SON1. During the vtransmission of impulses, `relay 2SD, a slow release type, is maintained operated by vii- 'i' tue ofthe above-described Aintermittent energization of its lower winding. After the receipt of the second impulse train, the above-described energizing circuit for magnet ZSM is {in al and the lower winding of relay 28D is deenergized. Relay ZSD thereafter releases.

Busy test.-ln order to prevent more than one of the plurality of calling connectors from seizing a given terminal set, means is provided in each calling connector for testing for busy condition on arselected terminal set. Ifk the busy Vtesting means fails to operate, other, switchthrough means within the connector is subsequently operated. The busy test is next described.

'Ifo any of the plurality of calling connectors being considered here, a busy -condition on a terminal set is indicated by the presence of a irst or `Vsecond marking signal on the busy test terminal of the selected set. The first andY second marking signals are (l) ground through any resistance up to the value of 1,000 ohms and (2) direct ground, respectively.l Accordingly, when the second impulse train has been received and the wiper set has engaged a particular terminal set, a test operation of the engaged vterminal set'is carried out during the time that relay 2SD is still inits operated condition. When relay ZSD. is operated, .a circuit for operating busy test relay ZBT is prepared from battery through the winding of relay 2BT, make contacts 2SD4, and wiper ZWS to the engaged terminal. In the event that direct or resistance ground is present on the terminal engaged by wiper ZWS, relay 2BT operates. Thereafter, relay ZSD releases in the] previously described manner and is effective in responseto the operation of relay 2BT for completing a locking circuit for relay .ZBT from ground through make contacts 2RD4, secondary off-normal contacts ZSONZ, and ZBTS, break contacts 2SD5, and the winding of relay ZBT to battery.

The operation of relay 2BT is effective for connecting busy tone to the calling line IL from busy tone through make contacts 2BT4, break contacts 2AL1, and the upper winding of relay ZCB to conductor TZ and thence to line 1L10. Thevparty at station A, upon hearing the tone, is infomed that he should return his telephone to itsv hookswitch so Vthat the switch train may be released in a manner to be described presently. The operation ofrelay BT is further effective for connecting 60 IPM battery through resistor 2K1 to incoming conductor ZHS atmake contacts 2BT1. Y Y

Switchthrough.-In the event that the terminal set engaged by the wiper set in 2the above-described manner fails to test busy, relay ZBT remains in its normal condition. 'Upon release of Arelay 2SD in the previously described manner, a circuit is thereupon completed for operating switchthrough relay 25W whichris traced over Vthe following circuit: .from ground through make contacts 2R'D4 and ZSONZ, break contactsrZBT and 2SD5, and the winding of relay 28W to battery. Relay 28W thereupon operates. 1

The switchthrough means comprising relay 28W is eiectivefor extending a connection from the incoming talking channel comprising incoming conductors 2T and 2R (to which theiirst calling line IL10 has been connectedfto the aforementioned talking channel terminals of 'the terminal set engaged by wipers ZWT and 2W?. at maker'contacts 2SW3 and 2SW4. Blocking capacitors ZCI and ZCZ are interposed between the incoming talkingchannel conductors and the wipers in order to separate the signaling channels including the talking conductor of the incoming end of the connector from the corresponding signaling channel at the outgoing end of the connector.

. Theoperation of relay ZSW is further eiective for marking Vthe selected terminal set in a first particular lmannenthat is, by applying ground through 1,000 ohms to the one of the terminals in the selected set engaged by wiper ZWS. This circuit is traced from ground through .1.000. ohm resistor, 2K3, break. contacts ZANBA,

make contacts 2SWS, and wiper ZWS to the terminal. This 1,000 ohm ground has the effect of marking the terminal set and its corresponding multiply connected terminal sets accessible to other calling connectors busy to other calling connectors within the above-referred to first plurality and for marking the terminal sets multiply connected thereto and accessible to answering connectors such as the one shown in Fig. 3 included in a second plurality as available. The operation of relay ZSW has the further effect of connecting conductor ZHSl, which is incoming from the common encoder control circuit shown in Fig. 6, to the one of the terminals engaged by wiper ZWHS at make contactsZSW. rPhe eectof this connection is to be explained presently.

The operation of relay 28W is further effective for operating start relay 2ST over a circuit which is traced from ground through break contacts ZRBZ, make contacts ZSWL break contacts ZNBl, ZANRZ, and 2AL4, and the winding of relay 2ST to battery. Relay 281` thereupon operates. The operation of relay 2ST marks the last step in the process of seizing the selected one of the terminal sets and is effective for starting the operation of the above mentioned encoder control circuit which is next described.

Operation of the encoder control Referring to 1, means including the above mentioned encoder control circuit shown in Fig. 6 is `common to the plurality of the calling connectors such as the ones shown in Fig. 2 and is effective in the manner presently set forth for energizing certain of the ones of the non-talking terminals selected by an operated one of lthe calling connectors. Upon the completion of the seizure of any one of the terminal sets to which the calling connectors have access, the seizing one of the connectors places a demand signal on the encoder control circuit, thereby causing a switch within that circuit to seize the terminal set on which are terminated conductors such as ZHSlt), 2li/[K10 and ZHFAlll incoming to individual ones of the calling connectors.

Starting the encoder control switch- Upon the operation of relay 28TH) within the seizing one of the calling connectors, a demand signal in the form of a ground connection is placed on the common start lead 2ST which extends -to contacts corresponding to 2ST4 within all calling connectors at make contacts ZSTf-i. The application of ground to conductor ZSTt) is eifective for energizing means comprising start relay 6ST for making the encoder control operative by completing an obvious circuit for start relay 6ST within the encoder control.

The operation of relay ST is -eiective for starting means comprising a single motion switch in operation by completing an operating circuit for hunt assist relay 6HA as follows: from ground through make contacts 6ST1, break contacts 6SW5, the winding of relay HA,

and break contacts 6MM. to battery. Relay 6HA thereupon operates with eifects to be explained presently. The operation of relay 6ST is also effective for preparing a circuit for energizing switchthrough relay W as follows: from battery through switch interrupter break contacts 6MM, the upper winding of relay 65W, make contacts 6ST2, break contacts 6TD4 and l-IAZ, and wiper 6WMK.

The above referred to single motion switch within the encoder control is of the well-known rotary type having a set of wipers including 69E/AL, 6WHS, and QSWMK, which may be advanced over first, second and third banks, respectively, of terminal sets. The switch is operated on a self-interrupting basis until the wiper set has been ad- -vanced into engagement with the terminal set on which are terminated the conductors incoming to the one of the calling connectors demanding service. To this end, upon the operation of relay dHA, a circuit is completed for energizing rotary magnet 6RM of the switch over the following circuit: from ground through break contacts TD2 and 6SW4, make contacts 6HA1, and the winding of magnet 6RM to battery. Magnet 6RM operates to open its own interrupter contacts 6MI1 and thereby release relay 6HA. Upon release of relay 6HA, the above traced circuit for preparing relay 68W is completed at break contacts 6HA2, and the above traced operating circuit for magnet 6RM is opened in order to deenergize that magnet. The deenergization of magnet 6RM is effective for advancing the wiper set of the rotary switch into engagement with the next succeeding terminal set in the banks.

This process is repeated until the wiper set is moved into engagement with the terminal set individual to the calling connector demanding service. The latter set is characterized by the connection of ground to the mark-r ingconductor from the calling connector circuit, in the case being considered here, conductor ZMKIO. Ground received over wiper WMK serves as a stop signal for the encoder control switch.

Stopping the encoder control switch-The engagement of Wiper 6WMK of grounded 2MK10 is eiective upon the next occurring release of relay 6HA for completing a circuit for operating switchthrough relay 6SW over the above traced circuitincluding the upper winding of relay 68W. Relay SSW operates to mark the end of the hunting operation of the rotary switch. Accordingly, the operation of relay 68W is effective for opening the above traced operating circuit for magnet GRM at break contacts 6SW4 in order to prevent the magnet from being reenergized. Similarly, the operation of relay 6SW is effective for opening the energizing circuit for relay 6HA at break contacts 6SW5 in order 'to release relay 6HA. Thereafter, neither relay 6HA nor magnet 6RM can be energized until a dismiss signal is received by the encoder in a manner to be described presently.

The operation of relay 68W is yfurther effective for preparing a release circuit for itself including the lower winding of battery at make contacts 6SW6. The operation of relay 68W is further eifective lfor completing an obvious operating circuit for switchthrough repeater relay 6SWR at make contacts 6SW3. Relay 6SWR, a slow operate type, operates at some time thereafter with effects to be explained presently. 'Ihe operation of relay GSW is further eective for opening an operating circuit for alarm repeater' relay 6ALR at break contacts 6SW1. The operation of relay 68W is further eifective for completing a holding circuit for itself including the upper Winding and wiper 6WNK at make contacts 6SW7. The operation of relay 68W is further effective for preparing a circuit for energizing wiper 6WAL at make contacts 6SW9. The operation of relays 68W and 6SWR is effective for transmitting a ground signal over conductor 6SY10 to the decoding matrices by co-nnecting ground to that conductor through break contacts TDl, make contacts 6SWZ, and 6SWR1 for purposes to be explained presently. Finally, relay 68W is included in start means operative for transmitting a signal for energizing one of the non-talking pair of terminals of the set selected by the presently engaged one of the calling connectors from ground through make contacts 6SW8, wiper 6WHS, conductor 2HS10, and, within the operated one of the calling connectors, make contacts 2SW6 and wiper 2WHS to the one of the terminals of the selected set engaged by Wiper ZWHS.

Selective operation of the encoder transmitter ZWHS. Each multiply connected terminal availableto a Wiper ZWHS of any calling connector is individual to .l0 one of a plurality of radio frequency receivers withinf a diiferent Subsystem. The subsystem including the calling connectors is accordingly arranged so that the'energization of any one such terminal is eifective'for -controlling a radio-frequency transmitter, shown in block form in Fig. 5d, common to the plurality of calling connectors in such al manner that the transmitter signals the radio frequency receiver corresponding'to the selected terminal. To this end, each multiply connected trans# mitter controlling terminal is connected individually to the positive side of a set of gating diodes, such as the ones shown in Fig. 5e, individual to that terminal. The other side of each diode within each set is individually connected to a certain one of a. plurality of inputs of a corresponding decoding matrix. Thus, the negative sides of diodes SDI, 5D2, and SDSA are connected to ones of the input conductors of the decoding matrices shown in Figs. 5a, 5b, and 5c, respectively. With this arrangement of elements, the energization of any one terminal accessible to a ZWHS wiper of any one of the calling connectors is effective for energizing a unique combination of matrix input conductors. In the case chosen for illustration here, it is assumed that wiper ZWHS has been advanced to engage the one of the terminals to whic conductor ZCI-1520 is connected.

Of the various sets of decoding matrix relays, only decoding matrix A is shown in any detail because decoding matrices B and C are substantially identical in function. In the contemplated system, it is necessary to energize one and only one input of each matrix in order to control the encoder-transmitter of Fig. 5d. The energization of less or more than this number of inputs gives rise toV an alarm condition, with results which are presently described. v

Upon the energization of conductor ZCHSZ() in the above described manner, one of the relays in each matrix is operated. In. the illustrated case, relay .SMA within decoding matrix A is operated overan obvious circuit. No other relay in matrix Afis to be operated at this time. Similarly, appropriate Arelays within matrices B and C-operate at this time. 1 The operation of one and only one relay in each of matrices A, B and C, a circuit is elfective for completing a start signal circuit to the encoder control shown in Fig. v6 and thereby operating sending start relay 6SS 'within-the encoder control. This circuit is`traced from battery through the winding of relay 65S, conductor 68810, make contacts 5MA2 on now operated relay SMA, break contacts such as 5MB1 and 5MN1 arranged in a chain as indicated in Fig. 5a, through conductor 6SYE10, corresponding contact sets in the decoding matrices B and C, conductors 6SY10, make contacts 6SWR1 and 6SW2, and break contacts 6TD1 to ground. vUpon receipt of the ground signal at Ithe windingof relay 68S, relay GSS operates to complete a locking circuit for start relay 6ST within the encoder control, so that the removal of a demand signal Afrom conductor 2ST10 will not prevent a complete operation of the encoder transmitter. The operation of relay 6SS is also effective to indicate to the encoder control that the matrices have been operated and therefore are ready to spill information into the encoder transmitter shown in Fig. 5d. This operation is next described.

Operation of the encoder transmitter The operation of encoder transmitter shown in Fig. 5d is described in general terms only because the encoder transmitter, as such, does not form a part of our invention. Upon the operation of sending start relay 6SS in the above described manner, a circuit is completed for transmitting a start signal to the encoder transmitter from ground through make contacts 6SW10 and 6SS2, conductor 6CL10 to the. encoder transmitter, and is effective for energizing means such as encoder transmitter start relay STS -over .an obviousV circuit.

YIl. Thereafter, means such as contacts SMSI are operated in response to the operation of relay STS and is effective for. transmitting a signal over conductor SMSlU to the decoding matrices for making the decoding relays in the various matrices effective to spill the stored information (i.e., the identity of the one of the radio frequency receivers to be signaled) into selective controlling means.

As previously pointed out, one of the decoding relays in each of matrices A, B and C is operated upon the registration of the identity of the terminal set selected by the calling connector. Each matrix has a plurality of output leads, one of which is to be energized upon the energization of the corresponding decoding relays. Each output conductor in each matrix is multiply connected to the corresponding conductor in each of the other matrices and Yto a corresponding plurality of input conductors to encoder transmitter d. Accordingly, when all matrices have been energized in the above described manner, a unique combination of three output conductors is energized. The input conductors of the matrices are connected to translating means such as the winding of a series of decoding relays SDMA through SDMN. Other means such as sequence switch 5SS10 is used for sequentially connecting battery to the other side of the winding of each decoding relay. Switch 5SS10 is made operative by means not shown to scan each decoding relay once upon each start signal sent to the encoder transmitter. With this arrangement the decoding relays within the encoder transmitter corresponding to the operated ones of the matrix relays are operated in sequence. The decoding relays are eifective for connecting corresponding ones of a series of control means such as SCMA through SCMN to a control point in radio frequency transmitter STRI. Transmitter STRI is thereupon selectively operated to transmit a coded signal from antenna SAN to all radio frequency receivers within the first subsystem. The transmitted signal, however, is unique to the'receiver of the paged party. It is the energization of unique combinations of matrix output conductors which causes encoder transmitter to be selectively energized in order to transmit a particular signal train.

In the illustrated case, it is assumed that the signal transmitted from antenna SAN upon the selective energization of encoder transmitter shown in Fig. 5d is effective for selectively signaling station IRF, shown in Fig. l. Upon receiving the signal unique itself, means at receiving station IRF is effective for informing the party at that station that a paging call is standing in for his station. The paged party then uses the telephone system to complete the paging call in a manner to be described presently.

Dsmssng the encoder control Upon the completion of transmission of a complete radio frequency signal, means, not shown, within the encoder transmitter is effective for operating end-of-cycle means such as contacts SEC1 which in turn are effective for transmitting a ground, end-of-cycle signal to the encoder control over conductor 6RS10. Apparatus, to be next described, is thereupon operated to release the encoder control from the one of the calling connectors del manding service and to deenergize the encoder transmitter.

The transmission of a ground, end-of-cycle signal over conductor 6RS10, an obvious circuit is completed for operating encoder dismiss relay 6TD. RelayTD thereupon operates. The operation of relay 6TD is effective for opening the above described circuit for operating relay 6SS at break contacts 6TD1. Relay 6SS thereupon releases with effects to ,be explained presently. The operation of relay 6TD is further effective for opening the previously described energizing circuit for rotary magnet 6RM at break contacts 6T D2 in order to prevent the energization of the magnet until the release process ofthe encoder control and encoder transmitter has been completed. The operation of relay 6TD is further eiective for opening the above described operating circuit for relay 6SW at break contacts 6TD4. However, make contacts 6SW7, which are in parallel with contacts 6TD4 cause relay 68W to continue to be operated at this time. The operation of relay 6TD is further effective for completing the previously mentioned release circuit for relay 6SW at make contacts 6TD3. As previously pointed out, relay GSW is operated and held by virtue of current flowing through its upper Winding. The release circuit for relay 68W comprises the lower winding of relay 68W and is effective for differentially energizing the lower winding with respect to the upper winding. The circuit is traced from ground through make contacts 6TD3 and 6SW6, the lower winding of relay GSW to battery. Upon the differential energization of both windings of relay 68W, relay 68W releases with effects which are to be explained presently.

Returning to the consideration of relay 68S, the release of relay 68S is effective for opening the previously referred to locking circuit for relay 6ST at make contacts 6SS1. Relay 6ST thereafter remains operated only by virtue of demand signals placed on start conductor by operated ones of the calling connectors. The release of relay 6SS is further effective for removing the start signal circuit for the encoder transmitter at make contacts 6SS2, so that the encoder transmitter is deenergized.

The release of relay 6SW10 is eiective for re-preparing the operating circuit for alarm repeater relay GALR at break contacts 6SW1. The release of relay 6SW is further eective for opening the operating circuit of relay GSWR. Relay GSWR thereafter releases with effects which are to be explained presently. The release of relay GSW is further effective for re-preparing the operating circuits of magnet 6RM and relay 6HA at break contacts 6SW4 and 6SWS, respectively. The release of relay 6SW is further effective for opening the above traced release circuit and the operating and hold circuit for relay 68W at make contacts 6SW6 and 6SW7, respectively. The release of relay 68W is further effective for opening the above traced energizing circuit for wiper GWHS at make contacts 6SW8. The release' of relay GSW is further effective for opening the above traced energizing circuit for wiper 6WAL and the start circuit for the encoder transmitter at make contacts 6SW9 and 6SW10, respectively.

The release of relays 68W and GSWR is effective for opening the above traced energizing circuit for relay GSS at make contacts 6SW2 and 6SW1.

After the removal of the energizing signal from the encoder transmitter, the above referred to end-of-cycle means within the encoder transmitter removes ground from the winding of end-of-cycle relay 6TD at make contacts SEC1, so that that relay may subsequently release. In the process of releasing the encoder control, 6TD is the last relay to be released owing to the fact that its winding is shunted by a high capacitance-resistance circuit also connected to battery. As a result, the reapplication of ground to the start relay 6ST winding prior to the complete dismissal of the encoder transmitter is without effect, because the operation of thev rotary selecting switch is prevented until the energizing circuit for rotary magnet GRM is recompleted at break contacts 6TD2. Similarly, relay GSW cannot be reoperated because its operating circuit is opened at break contacts 6TD4. Similarly, relay 6SS cannot be reoperated because its operating circuit is opened at break contacts 6T D1.

The removal of ground from wiper 6WHS within the encoder control is elfective for deenergizing the transmitter control terminal selected by the operated one of the calling connectors. The deenergization of the selected terminal is effective for removing the identifying signal from-the inputs to the various decoding matrices, thereby releasing the operated ones of the decoding matrix relays.

1f the paging call placed by the operated one of the 13 calling connectors has ,been answered at this time, the encoder control is free to respond to a subsequent demand signal from a different one of the plurality of calling connectors. In the event that the paging call mentioned above has not been answered, the encoder control rotary Answering a paged call As previously indicated, a paged party, upon receiving a signal at his station receiver, such as lRF, responds by calling into the special switching equipment from any telephone in the system. In the case chosen for illustration, it is assumed that the subscriber picks up the telephone at station B and thereby causes a connection to be extended to the switching equipment such as selector 1S20 in the conventional manner. Thereafter, the selector is directively operated by manipulating the dial at station B to cause selector 1S20 to select, and thereby to extend a connection to an idle one of a second plurality of answering connectors such as the one shown in Fig. 3. Thereafter the calling station B dial is further manipulated to cause the answering selector wiper set to engage a particular one of the multiply connected terminalsets accessible to the second plurality (answering) connectors. The terminal sets accessible to the answering connectors are also multiply connected to corresponding terminal sets which are accessible from the above described first plurality (calling) connectors.

Thus far in the description no indication has been given of the exact terminals selected either by the calling and answering connectors taken by the paging andpaged parties at station A and station B, respectively. This system is now explained in terms of the foregoing description. As indicated in the foregoing description, the calling connectors have access to a finite number of sets of terminals. In the contemplated system, one set of terminals is provided for each radio frequency receiver station within the above referred to first subsystem. Further, the numbers of the digits used to direct the calling and answering connectors into engagement with each terminal set correspond to the directory number of thepaged, first subsystem station. Thus a paging party, wishing to contact station S2, directs the conventional switching apparatus within the office to select an idle calling connector by dialing a first (calling) predetermined access code, and upon reaching the calling connector, proceeds to dial the directory number, that is, the digits 3 and 2 of the paged party into the calling connector. Thereupon the paging party has extended a connection from his station to a talking channel including the multiply connected ones ofthe terminals engaged by wipers ZWT and 2WR of the calling connector. The encoder transmitter is also operated in the above de- Yscribed manner at this time.

The paged party, upon receiving a signal from station receiver IRF, dials a second (answering) predetermined access code to direct the conventional switching apparatus within the telephone oice to select an idle one of the answering connectors. Upon reaching the answering connector, the answering party at station B dials his own rst subsystem station directory number (in this case 32) in order to advance the wiper set into engagement with the set of terminals corresponding to the ones engaged by the calling connector and to extend a talking connection from station B to the talking channel ones of the selected terminal set. Since both calling and answering connector wiper sets have been directed to corresponding, multiply connected terminal sets, a talking connection is completed between the paging and paged parties. It is obvious that within any time interval as many paging connections can be completed as there are pairs of calling and answering connectors, assuming that there are more terminal sets accessible to the connectors than there are connectors in any one plurality. The operation of the apparatus used to answer the call is next described in detail.

Seizz'ng the answering lconnecten-Referring to Fig. 1, it is assumed that the station telephone has been removed from its hookswitch, that a connection has been extended to selector 1820, and that selector 1S20 has been directively operated to extend a connection from calling station B to the incoming conductors shown collectively as 1C20 of the hitherto idle answering connector shown in Fig. 3. Upon the extension of ysuch a connection, an operating circuit for calling bridge relay SCB is completed. The circuit is traced from ground through break contacts SBT2, the upper winding of relay SCB, break contacts SSR1, conductor ST, the talking conductors of the office switching equipment and line 1L20, the station telephone including dial contacts at station B, the other conductors of line 1L20 and selector 1S20, conductor SR, break contacts SSR4, and the lower winding of relay SCB to battery. Relay SCB thereupon operates.

The operation of relay SCB is effective for closing an obvious circuit for operating release delay relay SRD at make contacts SCBI. Relay SRD thereupon operates. The operation of relay 3RD is effective for completing a circuit for energizing monitor lamp SML at make contacts SRD6. The operation of relay SRD is further effective for preparing an operating circuit for relay SSW at make contacts SRDS. The operation of relay SRD is further effective for opening the operating circuit for release magnet SRM at break contacts SRD4. The operation of relay SRD is further effective for completing a circuit for grounding incoming sleeve conductor SS at make contacts SRDS in order to hold the preceding switching equipment in operated condition Aunder the control of the answering connector. The operation of relay SRD is further effective for preparing an impulsing circuit for primary and secondary magnets SPM and SSM, respectively, at make contacts SRD1. The operation of relay SRD is further effective for completing operating circuits for primary and secondary delay relays SPD and SSD. The operating circuit of relay SPD is traced from ground through make contacts SRDZ, break contacts SPONl, and the upper winding of relay SPD to battery. The operating circuit of relay SSD is traced from ground through make contacts SRDZ, break contacts SSONl, and the upper winding of relay SSD to battery. Both relays SPD and SSD thereupon operate. Y

The operation of relay SPD is effective for preparing an energizing circuit for primary magnet SPM at make contacts SPDl, and for opening an operating circuit for secondary magnet SSM at break contacts SPDZ. Upon the operation of relays SPD and SSD, the answering connector is ready to receive first and second trains of directive impulses from calling line 1L20.

Primary advance of the answering c0nnecZor.-Relay SCB responds to trains of directive impulses in exactly the same manner as relay ZCB described in connection with the calling connector. In response to each release of relay SCB during the transmission of the rst train of impulses, a circuit is completed for energizing magnet SPM which is traced as follows: from ground through break contacts SCBZ, make contacts SRDI, SSDS, and SPDl, and the winding of magnet 3PM yto battery. Each energization of magnet SPM is effective for advancing the wiper set of the answering connector including wipers SWT, SWR, SWS, and SWHS, one additional step away l from the normal position in the primary direction of the switch.

The iirst step taken by the wiper set is effective for operating primary oit-normal means including various spring contact sets. Thus the above described operating circuit for relay SPD is opened at break contacts SPONl. In order to prevent relay SPD from releasing at this time, the lower, battery-connected winding of relay SPD is placed in parallel with magnet SPM. As a result, the lower winding of relay SPD is intermittently energized during the transmission of the first impulse train to the connector. Relay SPD is a slow release type, so that it remains operated during the time that magnet SPM is being intermittently energized. Upon the termination of the transmission of impulses of the lirst train, relay SCB comes to rest in its operated condition, thereby opening the above described energizing circuit for magnet SPM and the lower winding of relay SPD. Relay SPD thereupon releases because both its upper and lower windings are deenergized at this time.

At this point the wiper set of the answering connector has been advanced to a point opposite the required one of the levels of the plurality of terminal sets accessible to the answering connectors. Relay SPDhas been released, and relay SSD is operated. The answering connector is now in condition to receive a second directive train of impulses.

Secondary advance of the answering c0nnect0r.-The repeated release and reoperation of relay SCB during the transmission of a second impulse train to the answering connector is effective for completing an energizing circuit for means comprising secondary magnet ZSM upon each release of relay SCB for advancing the answering connector wiper set in a secondary direction. The circuit is traced from ground through break contacts SCBZ, make contacts SRDl and SSDS, break contacts SPDZ, and the winding of magnet SSM to battery` Each energization of magnet SSM is effective for advancing the wiper set of the answering connector one additional step away from its secondary normal position and into engagement with the next succeeding terminal set within the selected level.

The advance of the wiper set awayA from its normally secondary position is effective for operating secondary otinormal means including various contact spring sets. As a result of the operation of the secondary oli-normal means, the above described operating circuit for relay SSD is opened at break secondary oit-normal contacts SSONi. In order to maintain relay SSD operated during the transmission of the remainder of the impulse as in the second train, the lower, battery-connected winding of relay- SSD is connected in parallel with magnet SSM, so that relay SSD is intermittently energized during the transmission of the remainder of the impulses as in the second train. Relay SSD is a slow release type, so that' it does not release during each momentary deenergizationof itslower winding between impulses. Upon the transmission of the iinal impulse in the trainrelay SCD comesto rest in its operated position, so that the above described energizingicircuit for magnet SSM and the lower winding of relay SSD is opened at break contacts SCBZ. Magnet SSM therefore remains deenergized, and relay SSD then releases after a slight delay. At this point the wiper set has been advanced toengagc the required terminal set within the plurality of sets accessible to the answering connectors and calling connectors. As in the caseof the above described calling connectors, each terminal set accessible to one of the answering connectors, such as the one shown in Fig. 3, inclndes lirst and second talking channel terminals (engaged by wipers such as SWT and SWR) and a busy test terminal (engaged by a wiper such as SWS).

marks the seized terminal set and the corresponding terminal sets multiply connected thereto in a first manner by applying. a 1,000 ohm ground through conductor ZWS to the certain one of the non-talking conductors of the terminal set selected by the calling connector shown in Fig. 2. This signal on the corresponding, multiply connected terminal sets accessible to the answering connectors, indi'- cates to an operated one of the answering connectors that the terminal set is awaiting seizure by an answering connector. If the above described' answering connector of Fig. 3 encounters such a condition, switchthrough means within the connector is made operative, so thatV a talking connection is completed between the incoming conductors of the calling and answering connectors over the talking ones of the terminal sets accessible to both calling and answering connectors. This operation is to be described presently.

lf, on the other hand, the operated one of the answering connectors has been advanced to engage a terminal set on which a paging call between a pair of calling and answering connectors isalready in progress, the second answering connector is to be prevented from interrupting the already established connection. Accordingly, such a busy condition is indicated by the presence of direct ground on the one of the terminals engaged by wiper SWS. The ground potential is applied on that terminal in a manner to be described presently by the calling and answering con.- nectors already connected to the terminal set. In order to determine whether or not the engaged terminal set is busy, eachy answering connector is provided with busy test means comprising relay SBT immediately operative upon the engagement of the terminal set for detecting the presence of such a ground. The busy test means-in operated condition is elfective for preventing the operation of the switchthrough means within the answering connector and for applying busy tone to the line extended to that answering connector.

There is a third' possible condition of a terminal set upon the selection of the setby an answering connector, and that is this: the terminal set isy not then engaged by any one of the calling or answering connectors, so that the operated one ofthe answering connectors cannot complete a paging call by engaging that particular terminal set. Such a terminal set is unmarked, that is, the one of the set' engaged by the wiper corresponding to SWS has no potential at all standing thereon. In this event it is required that the operation of the switchthrough means within the operated one of the answering connectors be prevented and that busy tone be applied to the one of the lines extended to the operated answering connector. All three of the operations of the answering connector are nextdescribed in detail.

Busy test.-Assurr1ing rst that the selected terminal set has direct ground connected to the busy test terminal of the selected set, that is, the one of the terminals engaged by wiper SWS, after the transmission of theV secondv directive digit to the answeringconnector has been completed in the above described manner and before the release of relay SSD, a circuit is completed between wiper SSW and the battery-connected winding of busy test'relay SBT. The circuit is traced from wiper SWS, make contacts SSD6, and the winding of battery SBT to battery. The presence of ground on wiper SWS completes an obvious operating circuit for relay SBT. Relay SBT thereupon operates.

The operation of relay SET is eifective for transferring the calling subscriber line 1L20 from its connection to direct' ground through the upper winding of relay SCBZ into connection with the low impedance busy tone source at break contacts SBTZ and make contacts SBTI, respectively. Therefore busy tone is heard on station B connected to calling line iLZ. The operation of relay SBT is further effective in response to the subsequent release of relay SSD which takes place in the above described manner for closing a locking circuit for itself from ground through make contacts SRD2 and SBTS, break contacts SSDS, and the winding of relay SBT to battery. Relay SBT` thereforeremains operated so long as relay 3RD is held in operated condition, Tjhe operation of' relay SBT is, furtherv effective for preventing the switchthrough means comprising switchthroughv relay SSW from operating byv opening the operating circuit r including the lower winding ot relay SSW at break contacts vSBT6. Upon hearing the busy tone, thefcalling subscriber at station B returns his telephone to its hookswitch, so thatthe connection is released in the manner to be described presently.

Unmarked terminal set-*Assuming next that the terminal setY engaged' by thewiper setl of the operated 'answering connector is unmarked and' that no potential is present on the terminal engaged by wiper SWS', relay SBT fails' to operate in the above described manner and relay SSD subsequently releases.' At this time a second circuit rfor operating the busy'test means comprising relay SBT is completed from groundv through make contacts SRDZ and secondary oit-normal contacts SSONZ, rectier SRCT, breakl contacts SSWI and 3SD4, thermlistor 3TH, break contacts SSDS, andthe winding of relay SBT to battery. .The presence of thermistor STH inthe operatingcircuit of'rel'ay SBTis eiective fordelaying the operation of relay SBT' for a time interval greater. than, the

time required to operate switchthrough relay SSDQ'in" order to give relay SSW time to operate in the manner to be described presently. Thus, if a circuit is completed for operating relay SSW and,l the above described second operating circuit for relay SBT are completed at substantially the same time,y relay SSW operates rst Yand is eiiective for making the busy test means inoperativeV by opening the second operating circuit of relay SBT at break contacts SSWl. Assumingv that relay- SBT has operated over the above described second circuit, the operation ofY the vrelayis effective. in exactly the same manner to apply'busy tone to, theY calling hne 1L20 and station B, to complete a locking circuit for itself, and to preventv the subsequent,t operation of relay SSW.

Swtchthrugh-lt is next assumed that the wiper, set of the answeringA connector has selected a terminalset on which a 1,000 ohm groundgis presentA on the on'efo'f the, terminals. engaged by wiper SSW. Upon the completion of the transmission of the second impulse train to the answering connector,v such as theoneshownin'lfig. 3a, and prior tov the release of relay SSDQthe above described rst operating circuit for relayfSBT is Ycompleted at make contacts SSD6. Under thesey conditions,

Vthe 1,000 ohm ground prevents sufficient current to operate relay SBT from ilowingthrough the winding of that relay. Accordingly, relay SBT fails to operate duringthe time that relay SSD remains operated. 'thereafter relay SSD releases to completeafcircuit for operating the switchthrough meanswithin the connector comprising relay SSW in response to the s lection of a terminal set marked in the aforementioned rst manner. The operating circuit of relay SSW is traced from the marked terminal engaged by'wiper SWS,vbreak contacts 3SD7 and SBT6, make contacts SRDS, and the lower winding of relay SSW to battery, Relay SSW thereupon operatesA to the point where make contacts SSWS are closed. y Contacts SSWS in closed condition are effective a'gthisgtime for completing acircuit for fully operating, relay- SSW whichlis traced from ground through make, contacts SRD2 and SSWS, and the `upper winding ofgrelay SSW toL battery. Relay SSW thereupon fully operates.

The full operationV of relay `SSW is eiective. forcompletinga talking Achannel between the incoming, conductors SflandV SRA of the answering connector and4 the terminals engaged by wipers SWT and SWR at make contacts SSW7 Aand SSWS.YV Blockingv capacitors SC1 and SC2 in the lanswering connectorprevent .signaling current supplied yto lcalling line 1L20 from passing; through the multiple connection established over wipers SWT and SWR and vice versa. The operation of relay SSW is `also effective for connecting the ground-connected upper winding and battery-connected lower; winding ofrelay SSR`l to wipersfS-WT and SWR, respective1y,-at make con- :oper-ation of relay SSW is further effective for putting direct` ground on wiper SWS and its multiply connected, engaged terminal through make contacts SRD'Z and SSON2, rectiiier SRCT, and make contacts SSWZv to ,wiper SWS. Application Yof. direct ground. to wiper SWS `comprises a signalA for marking busy the engaged terminal set and any one of the corresponding terminal sets accessible from other answering and calling connectors.

Completing a connection between a calling and an answering connector Ati this point a connection has been completed between calling: line llLlt and its station A to the operated'one of the calling connectors such as the one shown in Fig. 2 andi a connection has been'compl'eted between answering lineVv 1L20 and its station B and the talking channel comprising `the multiple conductors connected to the ones of the terminalV set engaged by wipers SWT Vandv SWR of the operated answering connector such as the one shown in-Fig, 3. Thus the paging and paged parties at stations A and B, respectively, are now connected to each other. They above described applicationv of ground and'battery signals to wipers SWTZ and SWRVand the multiple conductortalking channel comprisesa signal for indicating to the correspondingy operated calling connector that the call has been answered. The multiple conductors extending between the terminal sets are connected so that the one of theconductors connected to the terminal engaged by wiper SWT isconnected to the terminal engaged by wiper ZWT, and so'that wiper SWR is similarly connected t0 Wiper ZWR. The application of ground in the above described manner to wipers SWT and ZWT and the application of battery to wipers SWR'and ZWR is hereinafter referred to as a normal supervisory signal, as coinpared to a later described reversesupervisory signal,

Referring to the calling connectors shown in Fig. 2, the calling connector includes means comprising normal battery relay Z'NB and reverse battery 2RB for detecting normal-"and reverse,y respectively, supervisory signals` appliedl to the paging systemV talking` channel.l The windings of" relays ZNB and ZRB are connectedin'series and (the `,combination bridged across the talking channel by break contacts 2SD'7 and ZSDS. With this arrangement, the signal-'detecting means is connected (and therefore made operativelonly after secondary delay relay ZSD has released at the'end of transmission vof the Vsecond directive digit tothe calling connector inthe previously described manner. Current flowing through the windings of" relays NBl and RB as the resultof the application of a supervision signal is suiiicient to operate either relay.

In ordento make relay ZNB only respond to the normal supervisory signal, thewinding of relay ZRB is shunted by rectifier 2RCT1 which is poled to short out the winding of relay ZRBl when theabovev described normal supervisorysignal yis, applied to wipers ZWT and ZWR. Similarly, in order to make relay ZRB onlyrespond to4 a reverse supervisory signal', the winding of relay ZNBY is shunted by rectifier ZRCTZ which is poled=-to `short out the-'winding of relay HB when the abovel described reverse supervisory signal is applied between'wipers ZWT and ZWR.

"Returning to the point where a normal supervisory lsignal is' applied between wipers ZWT and ZWR, relay ZNBfioperates` as indicated abovev '1`vhe1op'era'tionV of relayV ZNB is. effective for opening the` previously describedioperating circuit for start relay 2ST at break 19 contacts 2NB1. Relay 2ST, a slow-release type, releases thereafter. The operation of relay ZNB further is effective before the release of relay 2ST is completed for completing an operating circuit for answering supervisory relay 2AN which is traced from ground through break contacts 2RB2, make contacts ZSWI, ZNBZ, and 2ST3, and the winding of relay 2AN to battery. Relay 2AN thereupon operates. The operation of relay 2AN is elfective for closing an obvious locking circuit for itself at make contacts 2AN10 which are in parallel with make Vcontacts ZSTS, so that the subsequent release of relay 2ST is not effective for releasing relay 2AN.

The release of relay 2ST is elective for opening the previously described connection of rinkback tone to calling line IL at make contacts 2ST1 in order to inform the paging party at station A that this paging call has been answered. The release of relay 2ST is further effective in the previously described manner for opening the above traced operating circuit for relay 2AN at make contacts 2ST3. The release of relay 2ST is further eec- `tive for removing ground from the encoder control start conductor 2ST 10 at make contacts 2ST4, so that the encoder control start relay 6ST can release at this time if the Fig. 3 calling connector has been the only one of rthe iirst'plurality in operated condition and waiting for a paged party to answer. Referring to the encoder control shown in Fig. 6, the release of relay 6ST is effective for placing the encoder control in normal condition, so that it is thereafter free to respond to a demand signal from other operated ones of the calling connectors. In the event that connectors other than the one in Fig. 2 are inpperated condition and waiting for a paged party to answer, the release of relay 2ST is effective for removing the marking ground which identities the calling one of the calling connectors from marking lead 2MK10 at make contacts ZSTS. Thereafter, the rotary switch within the previously described encoder control is not stopped on the terminal set individual to the Fig. 2 connector, so that the encoder control is no longer elective for energizing the signaling terminal selected by the operation of the calling connector. For this reason, the selective control over the previously described encoder control exercised by the Fig. 2 calling connector is stopped when the paged party has answered.

The operation of relay 2AN in the above described manner is effective for reversing the direction of current ow within calling line IL10 and at calling station A at reversing contacts 2AN1, 2AN2, 2AN3, and 2AN4 in order to further indicate that the call has been answered. The operation of relay ZANis further effective for completing an operating circuit for answering repeater relay ZANR at make contacts 2AN7. The latter circuit is traced from ground through make contacts 2RD4 and v 2AN7 and the winding of relay ZANR to battery. Relay ZANR thereupon operates.

The operation of relay ZANR is effective for closing an obvious holding circuit for itself at contacts ZANRI which are in parallel with contacts 2AN7. The operation of relay ZANR is further effective for further opening the previously traced operating circuit for start relay 2ST at break contacts ZANRZ. -The operation of relay ZANR is further effective for transferring wiper ZWS from its previously traced connection to the 1,000 ohm ground into connection with direct ground at break contacts 2ANR4 and make contacts ZANRS. At this point direct ground is supplied to wipers ZWS and SWS at make contacts 2ANR3 within the calling connector and SSWZ within the answering connector, so that the busy condition on the terminal sets engaged by the calling and answering connectors of Figs. 2 and 3 is maintained upon the subsequent release of one or the other Vof vthe connectors. Both calling and answering connectors remain in the above described? conditions until the switch trains through which the connection has been established are released in the manner to be described presently. f

Alarm condition Thus far in the description of our system, it has been assumed vthat the control exercised by the paging party at station A over the calling connector yand decoding matrix has been effective to bring about the above described results. However, in the operation of the calling connector and encoder control, it is possible that the equipment will fail to function in the described manner. For instance, upon the application of an energizing signal to the one of the terminals engaged by wiper 2WHS within the calling connector, no relay or more than one relay within any one of the decoding matrices A, B or C might be operated. It is to be recalled that the proper operation of each decoding matrix requires the operation of one and only one relay. The following description of the alarm responsive apparatus is conlned to an example of misfunction within the decoding matrix where none or more than one of the decoding relays is operated. However, it is to be understood that the alarm responsive apparatus within the encodercontrol and individual ones of the connectors may be made to respond to other alarm conditions.

Misfultcton within the decoder c0ntr0I.-The contact vsets on the decoding relays are further arranged so that if two or more relays within each matrix relay are operated or if none of the matrix relays is operated, an alarm indicating conductor 6ALM10 is energized and the start conductor 6SS10 is not energized. Referring to matrix A shown in Fig. 5a, in the condition where none of the decoding matrix relays is operated, ground forwarded from the encoder control over conductor 6SY10 in the previously described manner is forwarded over the chainconnected break contacts such as 5MN1, SMBI, and `5MA1 to alarm conductor 6ALM10. In the condition where more than one relay within matrix A is operated, ground is'transmitted from conductor 6SY10 through the left-hand make contacts of a first operated relay in the chain and through the right-hand make contacts in the second operated relay in the chain. Thus, assuming that both relays SMN, and 5MB are operated within matrix A, ground extended to conductor 6SYE10, in the previously described manner, to alarm indicating conductor 6 ALM10 through make contacts' SMNZ, the right-hand, chain-connected break contacts of the succeeding vmatrix relays up to relay 5MB, and make contacts 5MB4 toconductor 6ALM10.

Forwarding an alarm signal for an operated connector.-The presence of a ground signal on alarm conductor 6ALM10 is asignal to alarm responsive means within the Fig. 6 encoder control. The operation of alarm responsive means including alarm relay 6AL and alarm repeater relay 6ALR is effective at this time (i.e., when the encoder control rotary switch has advanced its wiper set to engage the terminal set individual to the operated one of the calling connectors demanding service) for forwarding an alarm signal to the identified, operated one of the calling connectors. Alarm means within that connector thereupon is made effective for transmitting 'a dismiss signal to the encoder control and for notifying the paging party of the failure of the equipment to signal the paged party. Within the encoder control, means for releasing the encoder control from the particular one of the calling connectors is made operative. These operations are next described in detail.

The ground signal on conductor 6ALM10 is forwarded -by the encoder control through break contacts 6ALR3,

make contacts 6SW9, and wiper 6WAL to the conductors 2AL10 individual to the calling connector demanding service. The presence of ground on conductor 2AL10 is va signal effective for operating alarm relay ZAL over an obvious circuit. The operation of alarm relay ZAL with- ZAL to battery. 'Ihereafterirelay'ZAL is: maintained operated until a repairman operates keyfZRLK.`

The operation of relay ZAL'is further effective-for connecting busy tone from the low impedance busy tone source to the calling line ylLlOfby- Way of the upper Winding of relay 2CB at make contactsv 2AL2 and for disconnecting the direct ground connected to the upper winding of relay ZCB at break contacts ZALlf. The paging party at station A is thereby notified that the equipment is not capable of signaling the first subsystem receiver of the paged party and that the tc1ephone:at;station A should be returned to its hooksvvitch. The operation of relay ZAL is further effective for preparing a circuit including the upper Winding of relay ZPD for reoperating that relay upon the release of relay ZRD at make contacts 2AL3. The operation of relay ZAL isyfurther eectivefor releasing now operated sta-rt relay 28T-by opening the previously traced operating circuit at break contacts 2AL4. Relay 2ST thereupon releases. with etfects. which are to be explained presently. The operationsof relay ZAL is further effective for preventing the operation of release magnet 2RM by opening the operating circuit for the magnet at break contacts SEALS.. Therefore release vmagnet 2RM cannot be operated upon thel restoration of the calling station telephone to its. hookswitch, an event which would otherwise take placein the manner to be explained presently. The operation. of relay 2AL is fur-- ther effective for applying a ground signal. at make contacts 2AL6 to the no further alarm conductor ZNFAM), which extends from the encoder control to contacts similar such as ZALG in all other calling connectors, with edects which are to be explained presently.

Returning to the consideration of relay 2ST, the release of relay 2ST which is delayed owing toits slow release characteristics, is effective for disconnecting ringback tone from the calling line 1L2t) by opening the above traced connection at make contactsy ST1. Assuming that only the calling connector of Fig. 2 isoperated and sending a demand signal to the encoder control of this time, the release of relay 2ST is elfectivel for disconnecting ground from the encoder start conductor 28TH? at make contacts ZSTi. Similarly, the release of relay 2ST is further effective for removing ground from marking conductor ZMKlti at make contacts 2ST5.

Forwarding an alarm signal to thefcommon encoder contrl.-The ZNFAM) and the removal of ground from conductor 2ST1 are effective for operating alarm relay 6AL and releasing start relay 6ST Within the encoder control. The encoder control is thereupon in alarm condition. The op eration of relay 6AL is effective for prepari-ng a circuit for operating alarm repeater relay vSALR at make contacts ALi. The operation of relay 6AL is further effective for completing the release circuit of relay 65W from ground through break ycontacts GALRIi, make contacts SALE and 6SW6, and the lower winding of relay 68W to battery. Relay 68W is thereupon differentially energized in the previously described manner and releases. The operation of relay 6AL is further effective for operating alarm indicating means Within the encoder control comprising lamp 6ALL by completing an obvious circuit for energizing alarm lamp oALL at make contacts GALS.

The release of relay 68W Vis .effective for closing the prepared operating circuit for alarm repeater relay ALR from ground through make contacts 6AL1, vbreak contacts eSW, and the winding of relay ALR to battery. Relay ALR thereupon operates. The release of relay 68W is also effective in the previously described manner to open the ground connection to conductor 6SY1 at make contacts 6SW2, to release switchthrough repeater relay `GSWR by opening the latters operating circuit at make contacts 6SW3, toV reclose the. energizing circuits for rotary magnet GRM at break contacts tSSWA., to' reprepar'e the operating circuit for relay ol-IA at break contacts 6SW5 and to open the deenergizing circuit of application of ground to conductor- 22 relay GSWltl at break contacts: Sll/jfandy the ,holding circuit for relay 68W aty make contaets 6SW7.v The release of relay W is yfurther effective `for removing ground from Wiper ,6WHSfatmake-.contacts 6SW8,gfor opening the previously described energizing circuit. for the conector alarm relay ZAL at make contactsV 6SW9,and for opening the ground connection toconductor.A 6CL10 at make contacts 6SW10. Y j

Occurrence of a secondealarmcondtiomf-Upon the operation of relays 6AL and -ALR and the release of relays 6ST, 68W, and 6SWR, theA encoder control .is in condition to receive further demandsignals from operated ones of the calling connectors. The encoder Acontrol continues to be effective in the-previouslydescribed manner to energize ones of the terminal sets accessible to the calling connectors. With; relaysl lAL and- ALRfin operated condition, the occurrence `of a subsequent alarm condition of the above. described, type. relay 6TD is` ef.- fective for immediately placing the` encoder control in its dismissed condition in order to makev the encoder con.- trol available to the next subsequent operated one ,of the calling connectorsy demanding the services of the encoder control. This operation is 'next described in detail.

Assuming that relay-VGALR is inthe above indicated operated condition,V and that a: demand signal has been placed on conductor 2ST10 by an operated. one of the calling connectors, relay 6ST within .the .encoder control is again operated so that the rotary switch wipers of the encoder control are advancedinto engagement with the demanding one of the. plurality.' of: calling connectors. Thereupon relay 68W is again operated:v in the previously described manner in order to transmitan energizing signal over conductor 2HS10 tothe ,terminal set'selected' by the operated connector. The energiz'ation oftheselected terminal set is effective for transmitting anidentity signal to the decoding matrix.

It is assumed that one of the matrices misfunctions and that a ground signal is. again vplaced on alarm con'- ductor ALMtB in the previouslyl described Amanner. At this point the alarm signaL'instead of being transmitted to the operated one of-thefcallii'ig connectors demanding service by the encoder control aspreviously described, is diverted to the winding of relay 6TD atmake contacts oALRd. Relay 6TD is therefore operated at this time and is effective inthe previously described manner for opening the operating circuit forrelay 65S latV break contacts 6TD1, for opening the operating circuit of relay 68W at break contacts 6TD4, for opening the operating circuit for rotary magnet GRM at break contacts 6TD2 and for completing the release circuit forrelay 6SW at make contacts 6TD3. f

Thereupon relays 68S and 6SW are released in the previously described manner in orderto make the encoder control responsive to asubsequentlyV received demand signal from an operated one of the calling connectors. Relay 6TD thereafter releases in response to the release of the decoding matrix relays 'which takes place in the previously described manner and to v'the opening of the previously tracedV energizingtcircui't'for alarm conductor 6ALM10. Thefailure'-of relay SS'to operate at this time is effective'4 for withholdingV t-he start signal from the encoder transmitter `sta'rtmeansrand for preventing the operation of the'pr'viouslyfdescribed locking circuit for relay 6STat make contacts 6'SS2. and @SSL respectively. Therefore, the; vencoder transmitter is not operated at this time inI response i of the misfunctioning decoding matrix.

Release of the switch trainsv answering connectors included in the* pagingcall is novrmally under the control ofthecalldirecti'ng means `including the calling stations and Iincst,,1f-Releas'e ofthe to the `operation i Relay 2GB thereupon releases, opening the previously described circuit for operating release delay relay ZRD at make contacts 2CB1.

The release of relay ZRD is effective for opening the above traced operating circuits kfior-relays ZPD and ZSD and the previouslydescribed locking circuits for any of relays ZBT, ZSW, and ZANR at make contacts TRD-fl. As a result, any operated one of these relays is thereupon released. If relay ZBT has been operated, its release is 'effective for retransferring the upper winding of relay ZCB from its connection to the busy tone source into connection withV direct ground at make contacts EBT/i and break contacts 2B'I`3, respectively. It relay 25W has been operated, its release is effective for opening the above described operating circuit for normal battery relay ZNB and for disconnecting the incoming talking channel conductors of the connector includingr 2T and 2R from the wiper set at make contacts 2SW3 and ZSWQ. Relay ZNB thereupon releases. The release of relay 2SW is further effectivefor opening the above described operating circuits for relays 2AN and 2ST at make contacts.2SW1. Therefore either of relays 2ST or 2AN which has been operated is thereupon released. lf relay 2ANR has been operated, its release is effective for repreparing the operating circuit of relay 2ST at break contacts ZANRZ. The release of relay 28W is further effective forremoving both the direct and resistance ground connection to wipers ZWS at make contacts ZSWS. lf relay 2AN has been operated, its release is effective for rereversing the connection of the windings of relay ZCB to incoming conductors 2T and ZR at transfer contacts 2AN1-'2ANZ and `ZANS-ZANA.

The release of relay ZRD is effective in response to the previous advance of the wiper set away from its normal position andthe consequent operation of the previously describedV off-normal means for completing a circuit for energizing release magnet 2RM from ground through break contacts 2AL5, ZSWZ, and ZRDG, either or both operated, parallel-connected primary and second-- ary off-normal springs ZPONS and SONZ, respectively, and magnet 2RM rto, battery. The energization of magnet 2RM is effective for restoring the wiper set of the calling connector from its operated position to its primary and secondary off-normal positions. The operation of magnet 2RM is. further effective for applying ground to incoming sleeve conductor 2S at make contacts ZRMl in order to continue to apply busy marking ground to that conductor until the release of the connector has been completed. l

The return of the wiper set to its normal position is effective for restoring thetpreviously described olf-normal means of theconnector to their normal conditions, so that the above tracedoperating circuit for magnet 2RM is vopened at make contacts ZPONS and ZSONZ. Magnet ZRMIthereupon releases and removes the busy marking ground from ,conductor 2S at make contacts 2RM1.

At this pointtheoperated one of the calling connectors has been returned to `its normal condition. lt is thereafter available for reuse by other parties wishing to place paging calls. f

Attempted release of 'a calling connector after an alarm condition-If, after a paging party lhas operated one ofY the calling connectors, such as the one shown in Fig. 3,2and the attempt to place the paging call was unsuccessful owing to'the'occurrence of an alarm condi- .tion inthe previously described manner, the paging party returns ;the telephone toits hookswitch at station A.

Under these conditions, the switch train up to but not including the operated calling connector is to be released, and the connector is to be maintained in its operated condition until it is manually released in order to help the repairman locate the trouble-causing elements in the system. It is to be recalled that when the calling connector is placed in alarm condition, relays 2GB, ZRD, and ZAL within the calling connector are operated until the calling party hangs up. The hang-up operation of the calling party is effective in the previously described manner for releasing relays ZCB and 2RD.

The release of relay 'ZRD is effective in the previously described manner for releasing the preceding switch train including elements, such as selector 1810, by removing ground from incoming sleeve conductor 2S at make contacts ZRDS. However, relay 2AL is maintained in its operated condition through the previously described locking circuit including the break contacts or manually operable key ZRLK. The continued operation of relay ZAL is effective at this time for opening previously described energizing circuit for magnet 2RM at break contacts ZALS. Therefore, the wiper set of the calling connector is maintained in its operated position.

The operation of relay ZAL is effective in response to the release of relay ZRD for reoperating primary delay relay ZPD over a circuit traced from ground through break contacts 2RD3, make contacts 2AL3 and ZPONl., and the upper winding of relay 2PD to battery. Relay 2PD reoperates and is effective for reapplying busy marking ground to incoming conductor 2S at make contacts 2PD3. The application of ground to conductor 2S is effective for marking the calling connector busy to the switching equipment in the telephone office until relay ZAL is manually released.

After making an inspection of the locked up calling connector, the repairman manually operates key ZRLK in order to open the above traced locking circuit for relay ZAL at break contacts ZRLI. Thereupon relay 2AL releases. The release of relay ZAL is effective for opening the above traced second operating circuit for relay ZPD at make contacts 2AL3. Relay ZPD releases to remove ground from conductor 2S at make contacts 2PD3. The release of relay ZAL is also effective for completing the above traced circuit for energizing magnet 2RM at break contacts 2AL5. The calling connector wiper set is thereupon returned to its normal position and the connector is in normal condition, available to parties wishing to make paging calls.

Release of the answering connect0r.-lf, at the conclusion of a successful or unsuccessful attempt to extend a connection from a paged party at a station such as B through one of the answering connectors such as the one shown in Fig. 3, the answering party Wishes to discontinue the call, the telephone is returned to its hookswtch at station B, thereby opening the above described operating circuit for relay 3GB at the station hookswitch contacts. Relay 3GB thereupon releases and opens the above described operating circuit for relay 3RD at make contacts 3CB1. Relay 3RD thereafter releases.

The release of relay 3RD is effective for opening the previously described operating circuit for relays SPD, SSD, and SSW and the holding circuits for relay BBT at make contacts SRDZ. Any operated ones of these relays are thereupon released. If relay SBT has been operated, its release is effective for retransferring the upper winding of relay3CB from its connection to the busy tone source to connection with direct ground at make contacts SBTI and 3BT2, respectively. If relay SSW has been operated, its release at this time is effective for disconnecting the incoming talking conductors of the answering connector from the wiper set and for opening the previously traced operating circuit for relay SSR at make contacts BSW'Ii and 3SW8. lf relay SSR has been operated, it is released at this point. The release of relay SSR is effective for rereversing the connection of relay 3GB windings to inaciasaa coming conductors 3T and 3R at transfer contacts 38112- 3SR1 and 3SR3--3SRf-i. f

The release of relays 3RD and SSW is effective for completing an energizing circuit for release magnet SRM. The. circuit is traced from ground through break contacts 3RD4 and 3SW4, either or both, parallel-connected make contacts SPONZ and SSONS, and the winding of magnet `SRM to battery. The energization of magnet SRMA is etective for restoring the wiper set of the answering connector from its operated position to normal position. The energization of magnet SRM is also effective for applying busy marked ground to incoming sleeve conductor 3S at make contacts SRMl.

Upon the restoration of the wiper set to its normal position, the previously described primary and secondary Oifnormal means are also placed in normal condition so that the above described energizing circuit for Vmagnet 3RM is'opened at make contacts SPONZ and SSO-N3. Magnet SRM is thereby deenergized. The deenergization of magnet SRM is effective for opening contacts SRMl in order to remove ground from incoming sleeve conductor 3S. The answering connector is thereupon fully released. 4It is again available for use by paged parties in making calls.

' Intercept operation In the previous description, it has been pointed lout how a party, wishing to page', has caused a calling connector such as the one shown in Fig, 2 to be directively operated, with the result that the encoderv transmitter is selectively operated to signal the required party at a station in the radio frequency signaling system. It may be desirable in some instances to connect the paging party to an intercept answering device, such as the operator positiony indicated in Fig. 4b, immediately. Examples of calls requiring intercept services occur when the directory number of one of the radio frequency signaling system stations has been changed or discontinued, and when a' particular radio frequency signaling system station has been annoyed by persons placing repeated malicious calls to that station. In Ithe first instance, it is desirable to interconnect the calling party and the intercept operator and thereafter allow the calling party to release the switch train including the calling connector by the normal procedure which starts with hanging up' the calling telephone. ln the second instance, it is desirable to maintain the entire switch train including the calling connector operated after the calling party hangs up in order to allow a repairrnan to identify the calling line by tracing the call back through the switch train. ln order to meet these requirements, we have provided a single intercept termination adapted to our system which is capable of providing both types ofv intercept service.

An intercept termination shown in Fig. 4a is one of a plurality of similar terminations. Each such termination is accessible at a rst point to a terminal set to be given changed-number type intercept service by way of conductors such as those shown collectively as lLZi). The Same termination also is accessible at a second point to a terminal set to be given malicious-call type intercept service by way of another set of conductors shown colectively at 4lLltl. An operator position termination is provided which is common to the plurality of intercept terminations and used for connecting the operators telephone to the calling line. A detailed description of the intercept and operator terminations is next provided.

Malicious call intercept-Upon seizure of a terminal set by an operated one of the calling connectors which is connected to the second access point in the intercept termination, a supervisory signal of the reverse type described in connection with the steps involved in completing a connection between a calling and answering connector is applied to wipers 2W'I` and ZWR of the Fig. 3 calling connector. The reverse supervisory signal is achieved by connecting the battery-connected upper winding and the ground-connected lower winding of start relay 4ST to conductors T2 and 4K2 through break contacts 4LO1 and 4L'O2, respectively. Within the calling connector, relay 28W has already operated, so that the reverse supervisory signal is applied to the previously described supervisory signal responsive means including relays. ZRB and 2NB within the connector. As previously indicated, relay ZRB is operated in response to the application of the reverse signal to the talking channel of the calling connecten-while relay ZNB is not operated. In order to indicate the presence of a call standing in on the intercept termination, start'relay -E-ST within the termination operates in response to the flow of current through the calling connector supervisory means which includes the winding of relay ZRB.

Within the calling connector, the operation of relay RBZ is effective for opening the previously traced operating -circuit for answering relay EAN at break. contacts ZRBZ, so that relay ZAN may not thereafter be operated. The operation of relay 2KB is further effective for completing a holding circuit for relay ZRD at make contacts ZRB-l and through make contacts Z-RDl and the winding of relay ZRD to battery. The purpose of this holding circuit is to prevent the release of relay ZRD upon the release of relay ZCB and is further discussed in subsequent. paragraphs.

The extension of the connection from the terminal set Vof a calling connector to the lsecond access point of lthe intercept termination is further effective for completing a circuit for operating sleeve relay 4SL from ground through resistor 2K3, break contacts 2ANR4, make contacts ZSWS, wiper 2W, incoming sleeve conductor 4iSZ, resistor 4R31, and the winding of relay iSL to battery. Relay 4SL thereupon operates and is effective for preparing a holding circuit for lockout relay 4LO at make contacts 4SLl.

Returning to the consideration of the intercept termination shown in Fig. 4a, the operation of relay 4ST is Aeffective for applying ringback tone to the calling line through a circuit traced from the ringback tone source through break contacts 41u03, make contacts 4ST1, break contacts 4PU2, conductor RL and the talking channel of the preceding switch train including the calling connector. The operation of relay 4ST is further effective for completing a circuit for energizing incoming signal means comprising lamp llS over a circuit traced from ground through break contacts 4LOS, make contacts 4ST1, break contacts 4PU4, and the iilament of 'lamp 41S to battery. The operation of relay 4ST is further eiective for preparing an operating circuit for pickup relay PU at break contacts 4ST3. Relay 4ST also serves as means for gating the calls to the operator position, that is, to render call connecting means comprising relay PU individual tothe Fig. 4 termination eiiective and to make the PU relays in all other terminations inoperative. To this end, allPUl relays in the various intercept terminations are made to operate through a circuit including chain-connected contacts on thesta'rt relay such as 4ST. The operation of any 4ST relay opens the PU relaycperating circuits of all succeeding terminations at break contacts such as 4ST5. At the same time, the operationof the ST relay further prepares the operating circuit of the corresponding PU relay at contacts such as 4ST4.

In response t0 the energized incoming signal, an operator at the position indicated in Fig. 4b responds by extending a connection from her telephone 4TL to the common operator termination by inserting plug 4P into jack 4J over an obvious circuit. insertion of the plug into the jack also completesk an equally obvious circuit foroperating relay 48A.V

The operation of relay 48A is effective in response to the operation of gating means individual to one of the terminations such as relay 4ST for completing an operating circuit for the corresponding pickup relay such` as 4PU. The circuit is traced from ground through break contacts 4SB3, make contacts ftSAZ and 4S'l`4, break con 27 tacts 4PU5 and 4LO6, make contacts 4ST3, and the winding of relay 4PU to battery. Relay 4PU thereupon operates. The operation of relays 45A and 4PU is further eiective for completing a holding circuit for relay 4PU from battery through the Winding of relay 4PU, make contacts 4ST3, break contacts 45.06, make contacts 4PU6, and the parallel-connected make contacts 4SA3 and 4SB2 to ground. The operation of relay 45A is further effective Ifor opening an operating circuit for lockout relay 4LO at break contacts 4SA4. The operation of relay 4SA is further effective for completing an obvious operating circuit for relay 48B. Relay 45B thereupon operates.

The operation of relay 48B is eiective for preparing an operating circuit for relay LO at make contacts 4SB1. 'Ihe operation of relay 45B is further eitective for preparing an alternate circuit for holding relay 4PU at make contacts 4SB2. r[he operation of relay 48B is further effective for opening the above traced operating circuit for relay 4PU at break contacts 4SB3.

The operation of relay 4PU is further etective for disconnecting the above traced ringback tone connection from the calling line at break contacts 4PU2. The operation of relay 4PU is further etlective for completing the connection extended from the calling line through the operated one of the calling connectors and the operator position at make contacts 4PU1 and 4PU3. The operation of relay 4PU is further elective for opening the above traced energizing circuit for lamp 41S at break contacts 4PU4. The lamp is thereupon extinguished and remains extinguished throughout the remainder of the call. The operation of relay 4PU is further etective for opening the above traced operating circuit for itself at break contacts 4PU5. The operation of relay 4PU is further eiective for preparing an operating circuit for lockout relay 4LO at make contacts 4PU?.

At this point the station A on the calling line such as IL is connected to the intercept operator position. The

I intercept operator may thereupon monitor the connection. After monitoring the established connection, the operator may continue to hold the connection by leaving plug 4P in jack 4J until the connection has been traced. If the paging party hangs up during this interval, only the calling bridge relay, such as 2GB, within the calling connector is released. The switch train, including the calling connector, is maintained operated until released by the operator.

The operator withdraws from the monitoring connection by disconnecting her telephone from the intercept termination shown in Fig. 4b and thereby causing the operating circuit for relay SA to be opened. Relay 45A thereupon releases, opening the operating circuit of relay 48B at make contacts @SAL Relay 48B, a slow release type, releases at some time thereafter.

The slow release characteristics of relay 4SB insure that the above traced operating circuit of relay 4PU remains opened at break contacts 4SB3 until relay 48A is completely released and the operating circuit for relay 4PU further opened at make contacts 4SA2. During the time that relay 45B is still operated and relay 48A is released, a disconnect signal is transmitted to the intercept termination shown in Fig. 4a and is eiective for completing an operating circuit for lockout relay 4LO. The circuit is traced from ground through break contacts 4SA4,A make contacts SBl and 4PU?, break contacts 41.08, and the winding of relay `4LO to battery. Relay 4LO thereupon operates.

The operation of relay LO is eiective for completing a holding circuit for itself from `ground through make contacts 4SL1 and 4LO7 and the winding or relay -4LO to battery. Relay 4L() is therefore held operated under the control or relay iSL, which in turn is held'operated under the control of ground applied to incoming sleeve relay 4S72 from either calling or answering connectors. The operation or relay LO is eiectivefor removing 28 the reverse signal from the supervisory signal detecting means within the operated ones of the calling connectors by disconnecting the upper and lower windings of relay 4ST from conductors 4T2 and 4R1, respectively, at break contacts 41.01 and 41u02, respectively. Relay 4ST there,- upon releases.

The operation of relay 4LO is further effective for opening the above traced energizing circuit for lamp 41S at break contacts 4LO5 in order to prevent lamp 41S from being reenergized from this termination during the time that a calling or answering connector is being held on the terminal set individual to the intercept termination. The operation of relay 4LO is further effective for opening the above traced holding circuit for relay 4PU at break contacts 4LO6. Relay 4PU thereupon releases to disconnect the operator termination from the monitored connection at make contacts 4PU! and 4PU3.

The release of relay 4ST is ettective for reclosing they chain contacts for operating the pickup relays lin any of the plurality of intercept terminations at break con.- tacts 4ST5. Thereafter the operation of any start relay corresponding to relay 4ST in any of the other of the intercept terminations is etective for completing a circuit for the corresponding pickup relay.

Returning to the consideration of the incoming connector, after the removal of the reverse signal, relay ZRB is released. The release of relay 2RB is effective for repreparing the previously traced operating circuit for relay ZAN at break contacts Z'RBZ and for removing the holding ground from the Winding of relay ZRD at make contacts 2RB1. Thereafter the intercept call proceeds in the previously described manner.

Assuming however that the operator does not choose to withdraw from the connection and wishes to maintain the preceding switch train including the operated ones of the incoming connectors in its oit-normal position so that the identity of the calling line may be traced, the continued operation or relay 2SA prevents the closure of the operating circuit for relay 4LO. Consequently, the reverse signal continues to be transmitted to the operated one of the calling connectors extended to the Fig. 4a intercept termination. As a result relay ZRB is maintained in its operated condition in order to hold relay ZRD operated. lf during the time that relay ZRD is being held operated under the control of relay ZRD, the party at the calling station returns the telephone to the hookswitch of the calling station in order to release relays 2GB, the release of relay 2CE is without eiect because the previously traced release magnet operating circuit Within the connector is held open at break contacts ZRDS. Only after the intercept operator withdraws from the connection with the above described results, namely the release of relay RBZ, is relay ZRD released and the calling connector released in the normal manner.

Changed number call infercept.-Upon the extension of a connection from the operated one of the calling connectors to iirst termination access point over incoming conductors Tl and 4Rll of the intercept termination, a circuit is completed for supplying a normal signal of the previously described type to the signal responsive means within the operated calling connector through the batteryconnected upper winding and ground-connected lower winding of relay 4ST. Relay 4ST thereupon operates in the previously described manner. Thereafter the call to the intercept operator proceeds as described above, except that relay 4SL is not operated on this type of call, up to the point where the operator withdraws from the connection. During the time that the operators telephone is connected to the calling connector, the application of a normal signal to the talking channel of the connector is effective in the previously described manner for operating relay ZNB. Therefore the connector operates in the manner described in connection with answering a call placed to a normal terminal set. t v

Assuming that the party at the calling station returns 

